Spray an 8- x 8-inch baking pan with nonstick cooking spray and set aside.
Place the pretzels and cereal in a large bowl and set aside. In a small saucepan over high heat, combine the sugar, water, and corn syrup. Bring to a boil and cook for 3 to 5 minutes, until a candy thermometer registers 235º F. Remove from the heat and stir in the butter. Pour the mixture over the cereal/pretzel mixture and quickly stir until completely coated. Press the mixture over the bottom of the prepared pan and let cool to room temperature as you prepare the top.
For the top and assembly:
Combine the milk chocolate and peanut butter in the top of a double boiler placed over simmering water, stirring until the mixture is smooth. Pour the mixture over the cooled crust and spread into an even layer. Chill in the refrigerator for about 1 hour, until the layer is hardened.
Combine the bittersweet chocolate, butter, and corn syrup in the top of a double boiler placed over simmering water, stirring until the mixture is smooth. Pour the mixture over the cooled layer of milk chocolate and spread evenly. Chill for about 1 hour, until the glaze is hardened. Cut into squares or bars and serve at room temperature.